arXiv subjects
Publications and source records attributed to Andrew Yang.
An explicit subconvex bound for the Riemann zeta function $ζ(s)$ on the critical line $s=1/2+it$ is proved. Previous subconvex bounds relied on an incorrect version of the Kusmin-Landau lemma. After accounting for the needed correction in that lemma, we recover and improve the record explicit bound for $|ζ(1/2 + it)|$.
By combining and improving recent techniques and results, we provide explicit estimates for the error terms $|π(x)-\text{li}(x)|$, $|θ(x)-x|$ and $|ψ(x)-x|$ appearing in the prime number theorem. For example, we show for all $x\geq 2$ that $|ψ(x)-x|\leq 9.39x(\log x)^{1.515}\exp(-0.8274\sqrt{\log x})$. Our estimates rely heavily on explicit zero-free regions and zero-density estimates for the Riemann zeta-function, and improve on existing bounds for prime-counting functions for large values of $x$.
In 1848, Hermite introduced a reduction theory for binary forms of degree $n$ which was developed more fully in the seminal 1917 treatise of Julia. This canonical method of reduction made use of a new, fundamental, but irrational $\mathrm{SL}_2$-invariant of binary $n$-ic forms defined over $\mathbb{R}$, which is now known as the Julia invariant. In this paper, for each $n$ and $k$ with $n+k\geq 3$, we determine the asymptotic behavior of the number of $\mathrm{SL}_2(\mathbb{Z})$-equivalence classes of binary $n$-ic forms, with $k$ pairs of complex roots, having bounded Julia invariant. Specializing to $(n,k)=(2,1)$ and $(3,0)$, respectively, recovers the asymptotic results of Gauss and Davenport on positive definite binary quadratic forms and positive discriminant binary cubic forms, respectively.
Matching markets are of particular interest in computer science and economics literature as they are often used to model real-world phenomena where we aim to equitably distribute a limited amount of resources to multiple agents and determine these distributions efficiently. Although it has been shown that finding market clearing prices for Fisher markets with indivisible goods is NP-hard, there exist polynomial-time algorithms able to compute these prices and allocations when the goods are divisible and the utility functions are linear. We provide a promising research direction toward the development of a market that simulates buyers' preferences that vary according to the bundles of goods allocated to other buyers. Our research aims to elucidate unique ways in which the theory of matching markets can be extended to account for more complex and often counterintuitive microeconomic phenomena.
Given a positive integer $m\ge 3$, let $ch(m)$ be the smallest positive constant with the following property: \emph{ Every simple directed graph on $n\ge 3$ vertices all whose outdegrees are at least $ch(m)\cdot n$ contains a directed cycle of length at most $m$.} Caccetta and Häggkvist conjectured that $ch(m)=1/m$, which if true, would be the best possible. In this paper, we prove the following result: \emph{ For every integer $m\ge 3$, let $α(m)$ be the unique real root in $(0,1)$ of the equation} \begin{equation*} (1-x)^{m-2}=\frac{3x}{2-x}. \end{equation*} Then $ch(m)\le α(m)$. This generalizes results of Shen who proved that $ch(3)\le 3-\sqrt{7}<0.35425$, and Liang and Xu who showed that $ch(4)< 0.28866$ and $ch(5)<0.24817$. We then slightly improve the above inequality by using the minimum feedback arc set approach initiated by Chudnovsky, Seymour, and Sullivan. This results in extensions of the findings of Hamburger, Haxell and Kostochka (in the case $m=3$), and Liang and Xu (in the case $m=4$).